1. Field of the Invention
This invention relates to a process for preparing a copolymer of acrylonitrile and an aromatic vinyl compound having a well-balanced combination of color, transparency and softening point.
2. Description of the Prior Art
According to the conventional polymerization process for preparing copolymers of acrylonitrile and an aromatic vinyl compound in which an azo-type catalyst alone is used, the color of the resulting copolymer is good, but even when the polymerization system is heated to a temperature of 135.degree.C, the unreacted monomers do not decrease in quantity very much. As a result, the resulting copolymer has a low heat distortion temperature. When an organic peroxide catalyst is used alone, the resulting copolymer has a poor color.